Negative-lens type deflection magnifying means for electron beam in cathode ray tubes



Sept. 7, 1965 3,205,391

PE DEFLECTION MAGNIFYING MEA N. D. GLYPTIS NEGATIVE-LENS TY NS FORELECTRON BEAM IN CATHODE RAY TUBES Filed Nov. 18, 1957 5 Sheets-Sheet 1N. D. GLYPTIS 3,205,391 NEGATIVE-LENS TYPE DEFLECTION MAGNIFYING MEANSFOR ELECTRON BEAM IN CATHODE RAY TUBES Filed NOV. 18, 1957 5 sneetssheet 2 pmmm%w QflaQM $9,972

53 d WM Sept. 7, 1965 N. D. GLYPTIS 3,205,391

' NEGATIVE-LENS TYPE DEFLECTION MAGNIFYING MEANS FOR ELECTRON BEAM INGATHODE RAY TUBES Filed Nov. 18, 1957 5 Sheets-Sheet 3 Se t. 7, 1965 N.D. GLYPTIS 3,205,391

NEGATIVE-LENS TYPE DEFLECTION MAGNIFYING MEANS FOR ELECTRON BEAM INCATHODE RAY TUBES 5 Sheets-Sheet 4 Filed NOV. 18, 1957 Sept. 7, 1965 N.D. GLYPTIS I NEGATIVE-LENS 3,205,391 TYPE DEFLECTION MAGNIFYING MEANSFOR ELECTRON BEAM IN CATHODE RAY TUBES Filed Nov. 18, 1957 5Sheets-Sheet 5 INVENTOR. %0 s BY v w/v/zeyg United States PatentNEGATIVE-LENS TYPE DEFLECTIGN MAGNIFY- ING MEANS FOR ELECTRON BEAM INCATH- ODE RAY TUBES Nicholas D. Glyptis, Westchester, Ill. Multi-TronLaboratory, Inc., 4624 W. Washington, Chicago, Ill.)

Filed Nov. 18, 1957, Ser. No. 697,240 32 Claims. (Cl. 313-46) Thisinvention relates to a beam deflection device and more particularly toan improved beam deflection device in which the beam is projected towarda target followmg deflection.

In beam deflection devices, for example cathode-ray tubes, a beam isformed, shaped and deflected by suitable elements and is accelerateddirectly from the area of the deflection toward a target by a fieldwhich applies an accelerating force to the beam. One object of theinvention is to provide a novel beam deflection device in which theimage formed by a deflected beam is projected toward a target. The powerrequired to effect a given angular deflection of the beam is dependentto a large extent upon the velocity of the beam during deflection; andthis has placed an upper limit on the angle of deflection which may beachieved with conventional deflection which may be achieved withconventional deflection circuitry and components. By projecting thedeflected image in an enlarged configuration on the target, deflectionmay be accomplished at a low energy level. Another object is that theimage may be projected either by retracting or by reflecting the beamtoward the target.

Still another object is to provide a beam deflection device including abeam source, a target, means for deflecting the beam, means establishinga field condition for accelerating the beam toward the target, and meansfor modifying the field condition adjacent the deflecting means, withthe angle of incidence of the beam on the lines of force of the fieldbeing at least 90 throughout substantially the entire deflection range.A further object is to provide such a device in which the meansinterposed between the deflecting means and target establishes a fieldboundary condition adjacent the deflecting means.

Another object is that the field boundary condition is established bymeans of a grid interposed between the deflecting means and target andadjacent the deflecting means. Yet a further object is to provide a gridhaving alternate solid portions and openings in which the crosssectionaldiameter of the beam at the grid is greater than the area of an opening.

Another object is to provide a beam deflection device including a beamsource, a target for the beam, means for accelerating the beam along thefirst path, means associated with the first path for deflecting thebeam, means for reflecting the deflected beam along a second path, andmeans for accelerating the beam along the second path toward saidtarget. Yet a further object is to provide such a device in which thefirst path is generally parallel to the target and the second path isgenerally at right angles thereto. And another object is that thereflecting means includes a grid structure and a reflector plate mountedto intercept the beam in said first path.

Another object is to provide a beam deflection device including anenvelope, cathode, beam intensity control and beam shaping elements allcarried by supporting means in the envelope, means for establishing abeam deflection field carried by the supporting means, means forestablishing a field for accelerating the beam toward the target, and agrid carried by the supporting means and interposed between thedeflection means and target and adjacent the deflection means. A furtherobject is to provide a device in which the deflection establishing "Icemeans includes a member of insulating material carried by the supportingmeans and having conductive areas thereon.

Still a further object is to provide a device including a beam source, atarget, means for deflecting the beam toward desired positions on thetarget, means for establishing a field condition for applying anaccelerating force to the deflected beam, with the accelerating forceacting substantially along the path of the deflected beam, and means forvarying the intensity of the field condition for imparting a velocitymodulation to the deflected beam. Another object is to provide such adevice in which the field of varying intensity is established betweenparallel surfaces.

These and other specific objects and advantages of the invention will beapparent from the following detailed description and drawings, in which:

FIGURE 1 is a side view, partially in section, of a cathode-ray tubeembodying the invention;

FIGURE 2 is an enlarged fragmentary view of a portion of FIGURE 1;

FIGURES 3, 4 and 5 are diagrammatic views illustrating the eflect ofdifferent forms of grid surfaces;

FIGURE 6 is a diagrammatic view of a modified form or" the invention;

FIGURE 7 is a view similar to FIGURE 1 of another modified form of theinvention;

FIGURE 8 is a view similar to FIGURE 1 of a further modified form of theinvention;

FIGURE 9 is a fragmentary sectional view of another modified form of theinvention;

FIGURE 10 is a sectional view taken substantially along line 1fl-10 ofFIGURE 9;

FIGURE 11 is a sectional view of a beam deflection amplifier embodyingthe invention;

FIGURE 12 is a sectional view of another embodiment of the invention;and

FIGURE 13 is an enlarged fragmentary view taken generally along line13-13 of FIGURE 12.

While the invention is susceptible of various modifications andalternative constructions, it is herein shown and will hereinafter bedescribed in certain preferred embodiments. It is not intended, however,that the invention is to be limited thereby to the specificconstructions disclosed. On the contrary, it is intended to cover allmodifications and alternative constructions falling within the spirit.and scope of the invention as defined in the appended claims.

Although this invention is susceptible of application of many types ofbeam deflection devices, it is illustrated and will be described hereinprincipally in connection with cathode-ray tubes.

As pointed out briefly above, the deflection energy required for a givenangular deflection of a beam is a function of the velocity of the beamas it passes through the deflection region. In turn, the energy of thebeam itself is dependent on the velocity. For example, in a cathoderaytube the light output depends, among other parameters upon the velocitywith which the electrons of the beam impinge upon the surface of thescreen or target. Present commercial cathode-ray tubes represent, amongother considerations, a compromise between the desired light output andthe limitations of practical deflection. With the present invention thebeam may be deflected through a small angle to provide a relativelysmall image which is then projected on the screen of the tube. As acorollary feature of the invention, deflection is effected while thebeam has a relatively low velocity and the velocity of the deflectedbeam is increased before the beam strikes the target. Projection byrefraction will be discussed first.

Turning now to FIGURES l and 2, a cathode-ray tube is shown having anenvelope 21 on the interior surface of the face 21a of which isdeposited a suitable material, such as a phosphor 22. Mounted in theneck portion 23 of the tube 20 is an electron gun assembly, indicatedgenerally as 24, which includes a source of electrons, as a heatedcathode having an emissive surface, a control grid for varying theintensity of the beam of electrons emitted from the cathode and suitablebeam shaping elements. The phosphor layer 22, which luminesces when abeam of electrons impinge upon it, serves as a target or screen for thebeam.

A' deflection yoke assembly 25 is mounted on the neck 23 of the tube andincludes deflection coils which may be energized with suitabledeflection currents to scan the electron beam over the screen.Interposed between the deflection region, i.e. the region inside thetube bounded by the deflection coils, and the screen or target 22 is agrid 26 which may be of a wire mesh material.

Suitable operating connections may be made to the elements of theelectron gun through prongs 27 at the base of the tube and to the screen22 by means of the connector 28, extending through the wall of theenvelope.

As best seen in FIGURE 2, the grid 26 is connected, by means of aconductive coating 29, as Aquadag, a graphite-water glass emulsion,deposited on the interior surface of the envelope 21 and a conductor 30with one of the elements of the electron gun 24, as accelerating element31. Assuming that the cathode of the device is operated at or aboutground potential, a positive voltage of the order of 1,000 volts or somay be applied to the accelerating element 31 and thus to grid 26. Ahigher accelerating voltage, as of the order of 10,000-15,000 volts isapplied to the target 22 through the connector 28 and a high voltageconductive coating 32, deposited on the interior of the rear portion ofthe envelope. The high voltage conductive coating 32 is insulated fromthe grid 26 and the low voltage coating 2-9 by means of an insulatingcoating 33, as of chromic oxide. It will be understood that thethickness of the coatings 29, 32 and 33 on the interior surfaces of theenvelope is exaggerated in the drawings.

Inasmuch as the electron beam, when it enters the deflection region, hasbeen accelerated only to the extent of the voltage applied between thecathode and the grid 26, its velocity is relatively low and deflectionmay be achieved with a correspondingly small amount of power. The majorportion of the acceleration of the electrons in the beam occurs betweengrid 26, a boundry of the accelerating field, and the screen or target22.

The shape of the grid 26 and its relationship to the deflection region,and to a lesser extent its relationship to the screen of the tube,determine the refractive effect on the deflected beam of electronspassing through the field boundary. Three possibilities will bediscussed. In FIGURE 3, the grid 49 defines a surface which is a portionof a sphere and is so located that the center 41 of the spherical gridsurface coincides with the center of deflection, or the center of thedeflection volume, defined by the deflection coils 42. In this case, thedeflected beam 43 maintains its direction as it passes through the grid40. In FIGURE 4, the generally spherical grid surface is replaced by astraight or planar grid 44. With this construction, the electron beam 45is bent inwardly toward the center of the screen 46 as it passes throughthe grid; a positive lens effect. In FIGURE 5, the grid 47 is again agenerally spherical surface. However, the center 47a about which thegrid surface is formed is spaced away from the center 48 defined by thedeflection coils 49, in a direction toward the screen 50 of the tube. Inthis case, the electron beam 51, as it passes through the grid 47, isbent outwardly away from the center axis of the tube. This may bedescribed as a negative lens effect.

These various conditions may be described in another manner byconsidering the angle of incidence of the electron beam on theelectrostatic field between the accelerating field modifying grid andthe screen of the tube. If the beam enters the field in a directionnormal or generally at right angles to the field, the beam is not bentor refracted. This is the condition of FIGURE 3 and may be described asa zero lens effect. If the angle of incidence of the beam on theaccelerating field is less than the beam will be refracted or bentinwardly toward the center of the tube as shown in FIGURE 4. However,should the angle of incidence be greater than 90, the beam is bentoutwardly, FIGURE 5, in a manner which magnifies the effect of thedeflection field set up by the deflection coils. These effects aresometimes referred to herein as electron optical projection, or EOP.

It is believed that most applications of the invention will make use ofan accelerating field modifying structure which has either a Zero or anegative lens effect. However, it is to be understood that the shapes ofthe grids may be varied and a positive lens effect may be desirable insome cases, as where it is desired to compensate for an irregularity inthe face or screen of the tube, or for some other special purpose. Infact, a grid or grids having two or even all three characteristics mightbe used in a single device.

Returning now to FIGURE 1, the grid 26 is generally spherical and isformed about the center of deflection defined by deflection coils 25,providing a Zero lens effect. With the structure shown, a standarddeflection circuit such as used in television receivers, may be used toeffect scanning of a tube. The tube illustrated in this figure isrepresentative of the widest scan tube presently available commercially.The screen itself has a major axis of 20% inches, a minor axis of 16%inches and a diagonal dimension of 21 /3 inches. The depth of the tubefrom the outside of the face of the screen to the base 27, indicated at55, is 9 inches, while the distance from the face of the screen to therear of the deflection coils, indicated at 56, is 6 inches. In order toscan the screen of this tube, without the use of the accelerating fieldmodifying grid 26, it is necessary to use special deflection circuitry,including a water-cooled deflection yoke. With the accelerating fieldmodifying grid 26 the tube may be scanned with standard commercialtelevision receiver circuitry, using for example a 6BQ6 power amplifierin the horizontal sweep circuit and a 12BH7 in the vertical sweepcircuit.

FIGURE 7 illustrates how electron optical projection may be utilized toscan an ultrashort cathode-ray tube. The tube of FIGURE 7 has screendimensions comparable to those of FIGURE 1, however, the envelope 61 ofthe tube is much more shallow, the tube neck 62 is shorter and theelectron gun 63 is reduced in length. The overall dimension of this tubefrom the face of the screen to the base, indicated at 64, is 3% inches.The accelerating field modifying grid 65 has an ellipsoidal shapedesigned to provide a negative lens effect. The sweep circuits anddeflection coil 66 are designed to provide 150 scanning. However, withthe additional coverage provided by the negative lens effect of grid 65,the electron beam 67 scans an angle of on the screen of the tube.

The accelerating field modifying grid is preferably formed of a wiremesh material with relatively fine weave and small wire. For example,woven wire material with a 50 x 50 mesh, of wire 1 mil in diameter hasbeen found satisfactory. The wire is preferably stainless steel with acarbonized surface to reduce secondary emission effects. The grid may besecured in place in any suitable manner, as by porcelain cement.

It is preferable that the cross-sectional area of the electron beam asit passes through the accelerating field modifying grid be substantiallygreater than the areas of the openings between the grid wires, in orderto reduce undesired side effects, such as aberration. With the griddescribed above, the electron beam covers approximately four openingsbetween the wires of the grid. It should be kept in mind, of course,that when the beam is properly focused, so that it forms a sharp traceon the screen of the tube, its cross-sectional diameter is much greaterin the vicinity of the field modifying grid as it is not focused there.

Secondary electrons emitted from the grid are subject to a very strongaction from the individual lenses formed by the wires of the grid,scattering them at random through the tube where the majority strike theconductive interior coating and are dissipated. As the grid is spacedfrom the screen a substantial distance, any secondary electrons whichreach the screen arrive in a random fashion and at worst increase thebackground light level of the picture. They do not form an image on thescreen.

FIGURE 8 shows electron optical projection applied to a present dayexperimental tube designed for 150 deflection. The face of the tube hasa minor axis of 21.7 inches and a major axis of 26.3 inches. The overalllength of the tube from the face of the screen to the rear of the baseis of the order of nine inches. The grid 70 shown in the upper half ofthe tube is designed for straight-line projection, 01 a zero lenseffect, in connection with a deflection system including deflection coil71, designed for 150 scanning. The grid 72 shown in the lower half ofthe tube provides a negative lens effect in connection with a scanningsystem including deflection coil 73, designed for about 170 scanning.

FIGURE 6 shows a modification of the structures described above for usein a system employing velocity modulation of the electron beam. Again, abeam is deflected by suitable currents passing through coils 80 at a lowenergy level, as the grid 81 is operated at a potential much lower thanthat of the screen 82. A second grid 83 is interposed between the grid81 and the screen 82 of the tube. The grids 81 and 83 are parallel andare generally spherical in configuration, about the center of deflectionof coils 80. Connected between the grids 81 and 83 is an alternatingsignal source 84 which establishes a constantly varying potentialbetween the grids. This in turn causes bunching of the electrons as theypass between the grids, eifecting velocity modulation of the electronbeam. If desired, the velocity accelerating potential may be appliedbetween the grid 83 and the screen 82 of the tube or between the grid 81and the screen 82, if the grid 83 is eliminated, as shown in brokenlines. In order to achieve linear velocity modulation over the entirescan range of the deflection system, it is necessary that theaccelerating potential be applied between parallel surfaces so that thepath of the electron beam is normal to the lines of force of the varyingfield.

A combined beam deflection, velocity modulation device can be utilizedin magnetrons, klystrons, traveling Wave tubes and the like to achievean extremely wide frequency range with a single unit. For example, aklystron may have several cavities with a single electron beam source.Deflection means, as plates or coils, act on the beam to deflect ittoward a desired cavity. In passing from the deflecting means to thecavity, the beam is velocity modulated as described in connection withFIGURE 6.

The multiple grid structure of FIGURE 6 may also be used with gridshaving a negative lens eifect to achieve a desired degree of projectionof the image scanned by the beam in a series of steps. This ispreferable where projection is relied on to expand the size of the imagea substantial amount, as the distortion introduced by a series ofrelatively small refraction steps is less than that resulting from asingle refraction yielding the same end result.

FIGURE 9 illustrates another means for reducing the power necessary toeffect the desired deflection of the beam. The power required is afunction, not only of the velocity of the beam in the deflection region,but also of the volume of the deflection region, i.e. the volume withinthe deflection coils. Present magnetic deflection systems are limited byrequiring that the deflection coilsbe mounted on the outside of the neckof the tube. Thus the deflection volume may not be reduced more than ispermitted by the size of the tube neck, and this is also limited by thesize of the elements which make up the electron gun. In FIGURE 9, theelectron gun has mounted on the end thereof a tubular member 91 ofinsulating material, as glass. Formed on the surface of the tubularmember is a conductive area 92, which in the embodiment shown forms acoil. A similar coil 92a is provided on the other side of the tubularmember 91 while a second pair of conductive coils 92b and 920 are formedon the inside of the tubular member (FIGURE 10). Suitable connections(not shown) may be made to the ends of the coils 92, 92a, 92b and 92cthrough the neck of the tube and the prongs at the end thereof by meansof which the deflection currents may be applied to the coils. Thescanning field set up by these currents is thus concentrated in the areain which it is needed, im mediately adjacent the electron beam, and thedeflection volume of the system is substantially reduced, resulting in asaving in power.

In the case of an ultrashort tube, such as that shown in FIGURE 9, theelectron gun and deflection structur may extend from the neck of thetube 93 into the interior cavity of the envelope. If it is not practicalto achieve scanning of the screen 94 of the tube with straightdeflection, an accelerating field modifying grid 95 may be mounted onthe end of tubular member 91. In this case, the grid 95 preferably has anegative lens eifect configuration. It is preferable that the tubularmember 91 have a generally parabolic configuration, following theparabolic deflection path of the electrons as they pass through thedeflection field.

A tube combining the features of FIGURES 7 and 9 has no neck at all. Theentire electron gun and deflection system is inside the body of theenvelope, with only the connector pins extending therefrom.

FIGURE 11 illustrates the application of the principle of electronoptical projection to a beam deflection amplifier tube 100. In a beamdeflection tube, an electron beam formed from electrons emitted from acathode 101 is directed by potentials applied to deflection plates 102and 103 to one or the other of two anodes 104 and 105. An acceleratingfield modifying grid 106 is interposed between the deflection plates 102and 103 and the anodes 104 and 10S, and a voltage substantially lowerthan that of the anodes is applied thereto. As discussed above, thepower necessary to effect deflection of the electron beam issubstantially reduced, permitting the beam deflection amplifier tooperate with greater sensitivity.

FIGURE 12 illustrates reflective electron optical projection embodied ina cathode-ray tube 110, which has a target or screen 111 on one facethereof. The neck 112 of the tube, which houses the electron gunstructure extends from the edge of the tube envelope, rather than fromone of the major sides. Deflection coils 113 are provided about the neckof the tube for scanning the beam, and defining a deflection volumehaving a center of deflection 113a. Mounted at about the midpoint of theinterior of the wall of the tube opposite the screen or target 111 is areflecting structure 113 including a grid 115 and a reflector plate 116.

A positive accelerating voltage applied to grid 115 causes the electronsfrom the gun structure in tube neck 112 to accelerate along a firstpath, generally parallel with the tube screen 111. During traversal ofthis path, the beam is scanned by currents applied to deflection coils113 in such a manner that the desired image is formed on grid 115.Reflector plate 116 has applied thereto a positive voltage which islower than or negative with respect to the voltage applied to grid 115;while a final accelerating voltage, much higher than the voltage appliedto grid 115 is applied to the screen 111. Grid 115 is made up of a smallnumber of very fine wires, suflicient to establish the desiredaccelerating voltage along the first path, without interrupting asubstantial portion of the electron beams. Accordingly, as the electronbeam accelerates toward the grid 115, the greatest part of it passesthrough, whereupon it changes direction, as the reflector plate 116 isnegative with respect to grid 115, and is accelerated along a secondpath toward the screen 111. It will be noted that electrons scannedtoward the top of grid 115 (as viewed in FIGURE 12) along the path 118are reflected along a second path 118a, to the top of screen 111. Beamsfollowing the path 119 to the center of grid 115 are reflected along apath 11% to the center of screen 111 while electrons deflected alongpath 120 are reflected from the lower end of grid 115 along path 120a tothe lower portion of screen 111 The size and shape of grid 115 andreflector plate 116 are dependent on the shape, size and curvature ofthe target 111. As shown in the drawings, the grid and reflector platemay be round and slightly concave, in order to achieve the desiredreflecting characteristics.

A shield 121, which may be a grid-like structure, is provided betweenthe screen 111 of the tube and the first path of the electrons, betweenthe deflection zone and the reflecting means 114, to prevent the highaccelerating voltage applied to the screen from affecting the deflectionoperation.

In a tube with the cathode operated at about ground potential, reflectorplate 116 has a positive voltage of the order of several hundred voltsapplied thereto. Grid 115 is operated within the range of one-half totwo-thirds of the ultor or screen voltage which may be of the order of15,00020,000 volts. This isolating grid structure 121 is operated atground, or a low positive potential.

I claim:

1. A beam deflection device, comprising: a beam source; target means forsaid beam; means for deflecting said beam in two dimensions to desiredpositions on said target means; means establishing a field condition foraccelerating said beam toward said target means; and means modifyingsaid field condition adjacent said deflecting means, the angle ofincidence of said beam on the lines of force of said field being atleast 90 throughout substantially the entire deflection range of saiddevice.

2. A beam deflection device, comprising: a beam source; target means forsaid beam; means interposed between said source and target fordeflecting said beam in two dimensions toward desired positions on saidtarget means; means establishing a field condition for accelerating saidbeam toward said target means; and means interposed between saiddeflecting and target means for establishing a field boundary generallynormal to the path of the deflected beam and adjacent said deflectingmeans, the angle of incidence of said beam on the lines of force at saidfield boundary being at least 90 throughout substantially the entiredeflection range of said device.

3. A beam deflection device, comprising: a beam source; target means forsaid beam; means interposed between said source and target fordeflecting said beam in two dimensions toward desired positions on saidtarget means, said deflecting means having a center of deflection; meansestablishing a field condition for accelerating said beam toward saidtarget; means for establishing a field boundary adjacent said deflectingmeans and generally symmetrical with respect to said center ofdeflection, the angle of incidence of said beam on the lines of force atsaid field boundary being at least 90 throughout substantially theentire deflection range of said device,

4. A beam deflection device, comprising: a beam source; target means forsaid beam; means interposed between said source and target means fordeflecting said beam in two dimensions toward desired positions on aidtarget means, said deflecting means establishing a deflection volumehaving a center of deflection; means establishing a field condition foraccelerating said beam toward said target means; and means interposedbetween said deflecting and target means for establishing a fieldboundary adjacent said deflection volume and generally symmetrical withrespect to the center of deflection, the angle of incidence of said beamon the lines of force at said field boundary being at least throughoutsubstantially the entire deflection range of said device.

5. A beam deflection device of the character described in claim 4,wherein the said field boundary is normal to the path of said deflectedbeam throughout substantially the entire deflection range of the device.

6. In a beam deflection device: a beam source; a target; means fordeflecting said beam toward desired positions on said target; means forestablishing a field condition for applying an accelerating force tosaid dcflected beam, accelerating it toward said target, with theaccelerating force acting substantially along the path of said deflectedbeam throughout the deflection range of said device; and a source ofalternating electrical signal connected with said field condition forvarying the intensity of said field condition for imparting linearvelocity modulation to said deflected beam.

7. In a beam deflection device: a beam source; means for deflecting saidbeam to desired positions; means for establishing a field condition forapplying an accelerating force to said deflected beam, said meansincluding a pair of parallel surfaces, the accelerating force actingsubstantially along the axis of said deflected beam throughout thedeflection range of said device; and a source of alternating electricalsignal connected with said surfaces for varying the intensity of saidfield condition for imparting linear velocity modulation to saiddeflected beam.

8. In a beam deflection device: a beam source; means for deflecting saidbeam to desired positions; means for establishing a field condition forapplying an accelerating force to said beam, said means including a pairof parallel surfaces, one of which is a grid, the accelerating forceacting substantially along the path of said deflected beam throughoutthe deflection range of said device; and a source of alternatingelectrical signal connected with said surfaces for varying the intensityof said field condition for imparting linear velocity modulation to saiddeflected beam.

9. A beam deflection device of the character described in claim 8,wherein both of said parallel surfaces are grids.

10. The beam deflection device of claim 8, wherein one of said parallelsurfaces is a grid and the other is a target for said beam.

11. An ultrashort beam deflection tube, comprising: a target ofsubstantial surface area; an envelope having a face generallycoextensive with said target, mounting and enclosing the target, thedepth of said envelope being much less than the surface dimensions ofsaid face, said envelope defining a cavity; a structure including a beamsource comprising a cathode having a beam emissive surface and beamintensity control and shaping elements, beam deflection elements fordeflecting the beam in two dimensions to desired positions end saidtarget and a beam accelerating field control grid, said structure beingcarried by said envelope and extending into said cavity, saidaccelerating field control grid establishing a field boundary adjacentsaid deflection elements, the angle of incidence of said beam on thelines of force of said field being at least 90 throughout substantiallythe entire deflection range of said device.

12. A beam deflection device, comprising: a beam source; target meansfor said beam spaced along an axis from said source; means establishinga low potential zone adjacent said source; means establishing a highpotential zone adjacent said target and spaced from said low otentialzone, the projection of the spacing between said zones on said axisbeing small with respect to the spacing between the zones; meansoperatively associated with said low potential zone for deflecting saidbeam in two dimensions to desired positions on said target means; andgrid means at said low potential and positioned between said deflectingmeans and said space, modifying the field con- El formation in saidspace, the angle of incidence of said beam on the lines of force of saidfield being at least 90 throughout substantially the entire deflectionrange of said device.

13. A beam deflection device, comprising: a beam source; target meansfor said beam; means establishing a low potential zone adjacent saidsource; means establishing a high potential zone adjacent said targetand spaced from said low potential zone; means operably associated withsaid low potential zone for deflecting said beam toward desiredpositions on said target means, said deflecting means establishing adeflection volume in said low potential zone having a center ofdeflection; and an equipotential grid at said low potential interposedbetween said zones, adjacent said deflecting means and generallysymmetrical with respect to the center of deflection, the angle ofincidence of said beam on the lines of force of the high potential zoneadjacent said grid being at least 90 throughout substantially the entiredeflection range of said device.

14. A beam deflection device of the character described in claim 13,wherein said grid has a surface which is a portion of a sphere formedabout said center of deflection.

15. A beam deflection device, comprising: a beam source; target meansfor said beam; means establishing a low potential zone adjacent saidsource; means establishing a high potential zone adjacent said targetand spaced from said low potential zone; means operably associated withsaid low potential zone for deflecting said beam toward desiredpositions on said target means; and an equipotential grid at said lowpotential, having alternate solid portions and openings therein,interposed between said zones and closely adjacent said deflectingmeans, the cross sectional area diameter of the beam at said grid beinggreater than the area of said openings.

16. A beam deflection device of the character described in claim 15,wherein said beam diameter is several times the area of said openings.

17. In a beam deflection device: an envelope; mounting means in saidenvelope; a cathode having a surface for emit-ting a beam of electronscarried by said mounting means; a beam intensity control element carriedby said mounting means; beam shaping elements carried by said mountingmeans; a target for said beam in said envelope; means establishing a lowpotential zone in said envelope adjacent said mounting means; meansestablishing a high potential zone in said envelope adjacent said targetand spaced from said low potential zone; a member of insulating materialcarried by said mounting means in said low potential zone and havingconductive areas thereon for the application of electrical signals toestablish a beam deflecting field; and a grid carried by said mountingmeans, at a low potential, interposed between said zones and immediatelyadjacent said deflecting beams, the angle of incidence of said beam onthe lines of force of the high potential zone adjacent said grid beingat least 90 throughout substantially the entire deflection range of saiddevice.

18. The beam deflection device of claim 17, wherein said member ofinsulating material is tubular and has a generally parabolic surface.

19. A beam deflection device, comprising: a beam source; target meansfor said beam; means for deflecting said beam to desired positions onsaid target means; means establishing a field condition for acceleratingsaid beam toward said target means; and a mesh grid modifying said fieldcondition adjacent said deflecting means, the angle of incidence of saidbeam on the lines of force of the field at said grid being at least 90throughout substantially the entire deflection range of said device.

20. An expanded-sweep, beam deflection device, comprising: a beamsource; target means for said beam; means for deflecting said beam intwo directions to desired positions on said target means; meansestablishing a field condition for accelerating said beam toward saidtarget means; and a mesh grid modifying said field condition be- 16tween said deflecting means and said accelerating means, the angle ofincidence of said beam on the lines of force of said field being atleast throughout substantially the entire deflection range of saiddevice.

21. An expanded-sweep, cathode-ray tube, comprising: an electron beamsource; a sensitized screen providing a target for said beam; means fordeflecting said beam in two directions to desired positions on saidscreen; means establishing a field condition for accelerating saidelectron beam toward said screen; and a mesh grid modifying said fieldcondition adjacent said deflecting means, the angle of incidence of saidelectron beam on the lines of force of said field being at least 90throughout substantially the entire deflection range of said tube.

22. A cathode-ray tube having means for generating a cathode-ray beamand for directing the same along a predetermined path to a viewingscreen for use in a display system which includes a signal-actuateddeflection means spaced from the viewing screen for establishingdeflecting fields within the tube for scanning the beam in first andsecond mutually perpendicular directions, with said deflection meanshaving an effective deflection center, said tube including radiallysymmetrical electrostatic lens means constructed to produce a divergentmagnifying field within the tube, said electrostatic lens meansincluding an electrode composed of finely apertured conductive materiallocated between the effective deflection center and the screen in thepath of the beam and at least partially transparent to the electronsthereof, and an annularmember along the path of the beam beyond saidelectrode and adapted to be maintained at a potential higher than thatof said electrode, whereby said lens means produces a symmetrical fieldto refract the beam divergently with respect to the predetermined pathand magnify the scan thereof.

23. In a display system which includes a cathode-ray tube having anelectron gun for directing a cathode-ray beam along a predetermined pathfrom an electron source to a viewing screen, and deflection meanslocated between the electron source and the viewing screen fordeflecting the beam to scan the screen and having an effectivedeflection center, electrostatic negative lens means located between theeffective deflection center of said deflection means and the viewingscreen for producing within the tube an electrostatic field which isradially symmetrical about the predetermined path of the beam, saidelectrostatic field having components acting radially outward from thepredetermined beam path such that the effect of said lens means is torefract the beam divergently with respect to the predetermined path andmagnify the scan thereof.

24. In a display system which includes a cathode-ray tube having anelectron gun for directing a cathode-ray beam along a predetermined pathfrom an electron source to a target area, and which further includesdeflection means for establishing deflecting fields located between theelectron source and the target area for scanning the cathode-ray in afirst direction perpendicular to the predetermined path thereof and in asecond direction perpendicular to the first direction, said deflectionmeans having an effective deflection center, electrostatic negative lensmeans for producing a magnifying field located betweeen the effectivedeflection center of said deflection means and the target area, saidmagnifying field being radially symmetrical and having a divergentrefractive effect on the cathode-ray beam for magnifying the scanthereof in both the first and second directions.

25. A cathode-ray tube having means for generating a cathode-ray beamand for directing the same along a predetermined path to a viewingscreen for use in a display system which includes signal-actuateddeflection means spaced from the viewing screen for establishingdeflecting fields within the tube for scanning the beam in first andsecond mutually perpendicular directions, said tube including radiallysymmetrical divergent electrostatic lens means located to produce amagnifying field within the tube between the deflection means and saidviewing screen, said electrostatic lens means including a fieldterminating elect-rode composed of finely apertured conductive materialin the path of the beam and transparent to the electrons thereof,whereby the effect of said divergent lens means is to refract the beamdivergently with respect to the predetermined path and magnify the scanthereof.

26. A cathode ray tube comprising a vacuum-tight envelope having a neckportion, a faceplate portion, and an interjacent cone portion; meansdisposed within said neck for projecting an electron beam toward saidfacelate through a beam deflection region to scan said beam over saidfaceplate portion, a screen electrode on said faceplate, dome-shapedgrid elect-rode means disposed adjacent said deflection region andbetween said region and said screen for electrically shielding saidregion from said screen, the open side of said dome facing saiddeflection region, and a conductive coated electrode on said coneportion, said dome-shaped grid electrode being contoured to provide incooperation with said conductive coating electrode a supplemental radialdeflection electrostatic field.

27. A cathode ray tube comprising a target electrode, means forprojecting an electron beam toward said target electrode through a beamdeflection region to scan said beam over said target, terminal means forapplying a high positive potential to said target, multi-apertured gridelectrode means disposed adjacent said deflection region between saidregion and said target in the path of said beam for electricallyshielding s-aid region from said high positive target potential, hollowcylindrical electrode means disposed adjacent said multi-apertured gridelectrode means and between said multi-apertured grid electrode meansand said electron beam projecting means, and means for mounting saidmulti-apertured grid electrode and said hollow cylindrical electrodemeans in mutual electrical insulated relation whereby said hollowcylindrical electrode means may be electrically biased relative to saidmulti-apertured grid electrode.

28. In a display system which includes a cathode-ray tube having anelectron gun for directing a cathode-ray beam along a predetermined pathfrom an electron source to a viewing screen, and deflection meanslocated between the electron source and the viewing screen fordeflecting the beam to scan the screen and having an effectivedeflection center, electrostatic negative lens means located between theeffective deflection center of said deflection means and the viewingscreen for producing within the tube an electrostatic field which isradially symmetrical about the predetermined path of the beam, saidelectrostatic field having components acting radially outward from thepredetermined beam path such that the effect of said lens means is toretract the beam divergently with respect to the predetermined path andmagnify the scan thereof.

29. A cathode-ray tube which has a viewing screen and an electron sourcefor directing a beam toward the viewing screen, and which is adapted foruse with deflection means for establishing deflecting fields within thetube about an effective deflection center located between the electronsource and the viewing screen for deflecting the beam to scan the sameacross the screen, said tube including electrostatic magnifier meansproviding a radially symmetrical divergent electron lens located betweenthe position of said deflection center and the viewing Screen formagnifying the scan, and means providing focusing fields within the tubeof a sense and magnitude to compensate for the divergent effect of saidmagnifier means on the beam and thereby focusing the beam on the screen.

30. A cathode-ray tube which has a viewing screen and an electron sourcefor directing a beam toward the viewing screen, and which is adapted foruse with deflection means for establishing deflecting fields within thetube having an effective deflection center located between .the electronsource and the viewing screen for deflecting the beam t-o scan the sameacross the screen, focusing means associated with the electron sourceproviding a positive electron lens located between the electron sourceand the position of the effective deflection center for focusing thebeam, and mea-ns providing a radially symmetrical negative electron lenslocated between the effective deflection center of said deflectingfields and the viewing screen for magnifying the scan, said positiveelectron lens having suflicient convergent strength to compensate forthe divergent effect of said negative lens on the beam so that the beamis focused on the viewing screen.

31. In a display system which includes a cathode-ray tube having aviewing screen and means including an electron source for directing thebeam to the viewing screen, and deflection means for establishingdeflecting fields located within the tube between the electron sourceand the viewing screen for deflecting the beam to scan the screen, thecombination including, focusing means providing a focusing field locatedwithin the tube between the electron source and the deflecting fieldsfor converging the beam, and electrostatic means for providing aradially symmetrical divergent electron lens within the tube betweensaid deflecting fields and the viewing screen for magnifying thedeflection of the beam, said electrostatic means including a fieldterminating electrode located in the path of the beam and transparent tothe electrons thereof so that the effect of said electron lens means isto refract the beam and magnify the scan thereof, said focusing fieldhaving sufficient convergent strength to compensate for the divergenteffect of said magnifying electron lens on the beam so that the beam isfocused on the viewing screen.

32. A cathode-ray tube having an electron gun for directing acathode-ray beam along a predetermined path from an electron source to aviewing screen, said tube being adapted for use with deflection meansfor establishing deflecting fields within the tube having an effectivedeflection center located between the electron source and the viewingscreen for deflecting the beam to scan the same across the screen, saidtube having a radially symmetrical lens structure providing a radiallysymmetrical divergent electron lens located between the position of thedeflection center and the viewing screen and effective to magnify thescan of the beam, at least part of said lens structure being located inthe path of the beam and being at least partially transparent to theelectrons of the beam, and means establishing focusing fields within thetube effective to compensate for the divergent effect of said electronlens on the beam and thereby focusing the beam on the viewing screen.

References Cited by the Examiner UNITED STATES PATENTS 2,114,572 4/38Ressle-r 313-78 X 2,153,949 4/39 Varian 313-76 2,158,314 5/39Korshenewsky 313-78 X 2,225,455 12/40 Klauer 313-77 2,315,367 3/43Epstein 313-92 X 2,498,354 2/50 BOcCiarelli 250-161 2,617,077 11/52Schlesinger 313-78 X 2,632,864 3/53 Hunter 313-76 X 2,728,025 12/55Weimer 313-925 X 2,732,511 1/56 Dichter 313-181 2,770,748 ll/56Schlesinger 313-78 2,793,319 5/57 Nunan 313-925 X 2,795,729 6/57 Gabor313-78 X 2,795,731 6/57 Aiken 313-92 2,808,526 10/57 Davis 313-712,813,224 1l/57 Prancken 313-925 X 2,821,656 1/58 Foster 313-92 (Otherreferences on following page) References Cited by the Applicant UNITEDSTATES PATENTS GEORGE N. WESTBY, Primary Examiner.

1 3 UNITED STATES PATENTS 4/58 Hamlet 313-76 3/59 T116116 31510 2 150159 FOREIGN PATENTS 2,176,199 10/ 37 Great Britain 5 1 2 73 5 956 5/43Great Brltam. 91 6/36 France. 2755413 1/ 36 Germany. 42 8/53 Germany. 102892962 2/ 43 Italy. 9/37 Switzerland. 8/45 Switzerland.

RALPH G. NILSON, Examiner.

1. A BEAM DEFLECTION DEVICE, COMPRISING: A BEAM SOURCE; TARGET MEANS FORSAID BEAM; MEANS FOR DEFLECTING SAID BEAM IN TWO DIMENSIONS TO DESIREDPOSITIONS ON SAID TARGET MEANS; MEANS ESTABLISHING A FIELD CONDITION FORACCELERATING SAID BEAM TOWARD SAID TARGET MEANS; AND MEANS MODIFYINGSAID FIELD CONDITION ADJACENT SAID DEFLECTING MEANS, THE ANGLE OFINCIDENCE OF SAID BEAM ON THE LINES OF FORCE OF SAID FIELD BEING ATLEAST 90* THROUGHOUT SUBSTANTIALLY THE ENTIRE DEFLECTION RANGE OF SAIDDEVICE.